SCSI fixes on 20140819

These are the two bug fixes I mentioned in the final merge window pull.  One
 is a reversed logic check in the device busy tests which can cause a nasty
 hang and another crash seen in the new SCSI pool support if the use count ever
 goes to zero.
 
 Signed-off-by: James Bottomley <JBottomley@Parallels.com>
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Merge tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi

Pull SCSI fixes from James Bottomley:
 "These are the two bug fixes I mentioned in the final merge window
  pull.  One is a reversed logic check in the device busy tests which
  can cause a nasty hang and another crash seen in the new SCSI pool
  support if the use count ever goes to zero"

[ The device busy test already got merged from a patch earlier, so is
  now duplicated.  ]

* tag 'scsi-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/jejb/scsi:
  [SCSI] save command pool address of Scsi_Host
  [SCSI] fix qemu boot hang problem

drivers/scsi/scsi.c

@@ -377,6 +377,10 @@ scsi_alloc_host_cmd_pool(struct Scsi_Host *shost)
 		pool->slab_flags |= SLAB_CACHE_DMA;
 		pool->gfp_mask = __GFP_DMA;
 	}
+
+	if (hostt->cmd_size)
+		hostt->cmd_pool = pool;
+
 	return pool;
 }
 
@@ -421,8 +425,10 @@ out:
 out_free_slab:
 	kmem_cache_destroy(pool->cmd_slab);
 out_free_pool:
-	if (hostt->cmd_size)
+	if (hostt->cmd_size) {
 		scsi_free_host_cmd_pool(pool);
+		hostt->cmd_pool = NULL;
+	}
 	goto out;
 }
 
@@ -444,8 +450,10 @@ static void scsi_put_host_cmd_pool(struct Scsi_Host *shost)
 	if (!--pool->users) {
 		kmem_cache_destroy(pool->cmd_slab);
 		kmem_cache_destroy(pool->sense_slab);
-		if (hostt->cmd_size)
+		if (hostt->cmd_size) {
 			scsi_free_host_cmd_pool(pool);
+			hostt->cmd_pool = NULL;
+		}
 	}
 	mutex_unlock(&host_cmd_pool_mutex);
 }